Benign retroperitoneal schwannoma presenting as colitis: a case report

Abstract

We report a case of a patient presenting with clinical, radiological and endoscopic features of colitis due to a compressive left para-aortic mass. Total open surgical excision was performed, which resulted in complete resolution of colitis. Histopathology and immunohistochemistry revealed benign retroperitoneal schwannoma. These neural sheath tumors rarely occur in the retroperitoneum. They are usually asymptomatic but as they enlarge they may compress adjacent structures, which leads to a wide spectrum of non-specific symptoms, including lumbar pain, headache, secondary hypertension, abdominal pain and renal colicky pain. CT and MR findings show characteristic features, but none are specific. Schwannoma can be isolated sporadic lesions, or associated with schwannomatosis or neurofibromatosis type II (NF2). Although they vary in biological and clinical behavior, their presence is, in nearly every case, due to alterations or absence of the NF2 gene, which is involved in the growth regulation of Schwann cells. Both conditions were excluded by thorough mutation analysis. Diagnosis is based on histopathological examination and immunohistochemistry. Total excision is therapeutic and has a good prognosis. Schwannomatosis and NF2 should be excluded through clinical diagnostic criteria. Genetic testing of NF2 is probably not justified in the presence of a solitary retroperitoneal schwannoma.

Figure 1

Contrast-enhanced CT scan of the abdomen showing a diffuse infiltration around the rectum and the sigmoid colon, and thickening of their walls.

Figure 2

Well-demarcated, homogeneous mass measuring 60×50 mm in close proximity to the left iliac artery, lumbar vertebrae and psoas muscle, on contrast-enhanced CT scanning.

Figure 3

Coronal T₁-weighted MR image using gadolinium, showing a solid mass with the same features as seen with CT scanning.

Figure 4

Perioperative examination of the mass revealed a solid, greyish, ovoid tumor with a smooth capsule and a homogeneous yellow core.

Figure 5

Antoni A area on the right (well-organised spindle cells in a palisade pattern) and Antoni B area (less cellular, loose pleomorphic cells) on the left (HE, × 200).